The discovery in 1985 of the so-called ``Ozone Hole'' has increased concerns around the world on the stability of the stratospheric ozone layer, which shields the earth from harmful ultraviolet radiation. Aircraft missions to Antarctica in 1987 (Airborne Antarctic Ozone Experiment; AAOE) and to the Arctic in 1989 (Airborne Arctic Stratosphere Expedition; AASE I), together with numerous ground-based measurements, have provided first order answers to the causes of the Ozone Hole. The aircraft expeditions established that, contrary to expectations, that the chemical removal of ozone by chlorine-catalyzed cycles is enhanced in polar regions during winter and spring. It is now recognized that heterogeneous chemical reactions on the surfaces of solid nitric acid and ice particles (Polar Stratospheric Clouds Type I and II, respectively) that form in the polar stratosphere in winter as a result of the extremely cold temperatures during that season are the main culprits in creating the highly reactive form of chlorine, Chlorine Monoxide (CLO) which removes ozone from that region. In the following we review some of the recent microphysical studies of these important cloud types. Toohey [1995] in this issue reviews the relevant chemistry studies related to ozone depletion in the polar stratosphere. Special issues of Geophysical Research Letters [March Supplement, 1990] and Journal of Geophysical Research [30 May 1992] have been devoted to the research results focussed on the ``Ozone Hole'' problem.